Dose response of the A/Alaska/77 (H3N2) ca reassortant virus was completed this year. The human infectious dose 50 was 10 5.5 TCID 50. The presence of local nasal wash, IgA anti hemagglutinin antibody correlated with resistance to infection with vaccine virus. The A/HK/123/77 (H1N1) ca reassortant induced resistance to wild type virus infection in seronegative adults. The A/Cal/10/78 (H1N1) ca reassortant virus was attenuated, genetically stable, and non-transmissible in seronegative adults. The HID 50 was about 10 6.2 TCID 50. The A/Washington/897/80 (H3N2) ca virus was also attenuated in seronegative adults. Febrile illness occured when vaccines were administered a dose of approximately 10 7.5 TCID 50 of ca virus but the frequency was usually less than 5 percent of susceptible vaccinees. Immunological memory in the IgA isotype was demonstrated for the upper respiratory tract. During primary infection of adults serum antibody occurs in IgG, IgA, and IgM isotypes, but during secondary infection antibody occurs mostly in IgA and IgG isotypes. The magnitude of IgA antibody produced in the local respiratory tract correlates with that in serum of individuals infected with influenza A virus.